It integrates with nfqueue on Linux and a kernel extension on Windows. It does not use a virtual interface.
The SPN (Safing Privacy Network; VPN alternative) is optional.
More details on the docs: https://docs.safing.io/
I have a VPN configured in my pfSense router so that I don't need to run it in each client. I guess this would make it easy to go over the 5 device limit though...
Regardless, I'll try out for the firewall and network monitoring.
The device limit is hard, but we need to limit usage somewhere, as we don't see how much bandwidth one user uses.
Can you elaborate on your use case where you have more than 5 devices?